To investigate the response of N₂O emission in wheat field to the gradually elevated CO₂ concentration and the reduction of nitrogen fertilizer application,we conducted field experiments using Yangmai 22 as the experimental material.The experiments were carried out on a field equipped with an automatic CO₂ concentration control platform formed by Open-Top Chambers (OTC).Under the condition of ambient atmospheric CO₂ concentration (AC),a treatment of gradually elevated CO₂ concentration (EC) was set up,which increased by 40 μmol·mol^-1 annually from the winter wheat growing season of 2016-2017,reaching 120 μmol·mol^-1 higher than AC in the wheat growing season of 2018-2019.The nitrogen fertilizer treatments were set as a conventional level (N₁,25 g·m^-2) and a reduced level (N₂,15 g·m^-2).The N₂O fluxes were measured by a static opaque chamber-gas chromatograph method.The results indicated that throughout the winter wheat growing period,the changes of N₂O emission from winter wheat field were relatively consistent for all treatments with an overall fluctuating downward trend.No significant effect of EC treatment on N₂O emission was observed during the winter wheat growing seasons.While the N₂ treatment significantly reduced the cumulative N₂O emission by 45.2% compared with the N₁ treatment (P=0.004) under the AC,which was not significant under EC treatment.The impact of nitrogen reduction on N₂O emission was evident during winter wheat stage from booting to milking.Under the combined effect of gradually elevated CO₂ concentration and reduced nitrogen fertilizer application,the latter was the main factor affecting N₂O emission in winter wheat field.